Tanks in various shapes are used in liquefied gas carriers for marine transportation of a liquefied gas. Among these tanks, there is a case where a horizontal type cylindrical tank is supported by a pair of saddles spaced apart from each other in the axial direction of the tank. Each saddle has an arc-shaped supporting surface extending along the outer peripheral surface of the tank so that even when the ship oscillates (in a case where the axial direction of the tank coincides with the ship length direction, even when the ship rolls), the saddles can receive the load of the tank including the contents therein.
For example, Patent Literature 1 discloses a support structure of a tank, in which support units are interposed between the tank and supporting surfaces of respective saddles. Each support unit includes: a reinforcing plate joined to the outer peripheral surface of the tank; partition walls arranged on the reinforcing plate in the circumferential direction of the tank; a pair of holding plates disposed on both sides of the partition walls; and block-shaped thermal-insulating liners fitted in respective rectangular spaces surrounded by the partition walls and the holding plates, the thermal-insulating liners being in contact with the supporting surface of the saddle. The tank, other than its portions supported by the supports units, is covered with a thermal-insulating material.
Since a liquefied gas to be stored in the tank is a low-temperature gas, when the liquefied gas is fed into the tank, thermal contraction of the tank occurs. The thermal-insulating liners in the support structure disclosed in Patent Literature 1 are divided up in the circumferential direction of the tank so that a reduction in the diameter of the tank (i.e., deformation of the tank in its radial direction) due to the thermal contraction can be accommodated. Cuts are made in both ends of each thermal-insulating liner in the circumferential direction. The cuts in adjoining thermal-insulating liners form a groove, which is open toward the supporting surface of the saddle. A flexible thermal-insulating material is disposed in the groove.
Patent Literature 1 gives a description implying that when a reduction in the length of the tank (i.e., deformation of the tank in its axial direction) occurs due to thermal contraction, displacement of one of the support units in the axial direction of the tank is restricted while the other support unit is allowed to slide. This is based on the following technical feature: since the thermal-insulating liners are block-shaped, the thermal-insulating liners can follow the tank and are thereby displaceable in the axial direction of the tank without requiring any special measures.